Vehicle restraints are utilized to increase safety at a loading dock. The restraints secure a truck trailer to the dock when loading or unloading the trailer. The restraints typically engage a rear horizontal bar referred to as the rear impact guard (RIG) or ICC bar. The RIG or ICC bar is located at the rear end of the trailer below the trailer bed. When the trailer backs up to an available loading dock stall, the ICC bar is positioned close to the face wall of the dock. Bumpers typically extend from the face wall to protect the trailer and dock. Trailer restraints typically include a hooking device located in front of the dock and anchored to the dock or ground. When in use, the hooking device forms a barrier in front of the ICC bar to secure the trailer so it cannot move away from the dock. The restraint helps avoid accidents by securing the trailer to the loading dock so the truck driver does not inadvertently pull the trailer away when the trailer is being loaded or unloaded. The restraint also helps prevent the trailer from being pushed away from the dock during the process of loading and unloading the trailer. For example, when a fork lift carrying heavy cargo rides onto the trailer and abruptly stops, the trailer tends to move away from the dock.
Conventional trailer restraints include storable restraints and impact restraints. Storable restraints move between a raised operating position and a lower stored position. When in the stored position, a trailer backing into an available loading dock stall should clear the device. Conventional storable restraints are disclosed in U.S. Pat. Nos. 4,488,325, 5,096,359, 4,964,777 and 7,384,229. When the trailer and dock leveler are properly positioned with the lip of the leveler resting on the trailer bed, the stored restraint is activated to rise up and securely engage the ICC bar. Restraint mechanisms of this style are powered into their raised position by motors, springs, or other mechanical means.
Impact restraints include a movable carriage that adjusts to the height of the trailer ICC bar. The carriage includes a pair of spaced shear plates that hold a selectively rotatable hook as shown in FIG. 1. The front ends of the shear plates form a ramp or sloped portion of the carriage. The hook is stored between the plates and behind the ramp. When a trailer backs into an available stall, the ICC bar engages the ramp. As the trailer continues backing into the stall, its ICC bar pushes the ramp and carriage down until the ICC bar engages a flat top portion of the carriage. The ICC bar then moves along this flat top portion until the bar is aligned above the hook as disclosed in U.S. Pat. Nos. 4,264,259, 4,560,315, 6,162,005 and 8,596,949. The carriage has a drive system with a motor to rotate the hook. An operator actuates the motor when the ICC bar is aligned over the hook. The motor rotates the hook so that it emerges from the carriage and securely engages the ICC bar to hold it in a secured or locked position.
A problem with conventional impact restraints is that some trailers have an ICC bar with a sharp rearward facing lower edge. This sharp edge can bite into and damage the ramp as shown in FIG. 1. Resolving this situation is problematic. The hook is carried between the shear plates. Any design must allow the free movement of the hook. Fixing a ramp between the spaced shear plates is not feasible as this will obstruct the deployment of the hook. Increasing the thickness of the shear plates is cost prohibitive as the plates are relatively large and the added weight would reduce the effectiveness of the biasing springs to ensure the carriage and hook remain engaged with the trailer during use.
Another problem with conventional impact restraints is that the carriage is biased to a raise home position a predetermined height above the ground. While most trailers have an ICC bar located at a height that allows the bar to engage the ramp formed by the shear plates, some trailers locate the ICC bar lower than normal. Accordingly, the shear plates hold a leg or toe extension that extends the length of the ramp to accommodate these lower ICC bars. The upper end of the ramp leg is rotatably secured between the shear plates. The leg must freely rotate between its ramp forming and collapsed positions. When the ICC bar pushes the carriage down to a position where the lower end of the leg hits the ground, the leg must rotate forward into a collapsed position. If leg rotation is obstructed, the trailer ICC bar will not properly engage the flat upper surface of the carriage to allow proper deployment of the hook, or the trailer can ride up onto the carriage with the weight of the trailer pressing down on and damaging the restraint.
Another problem with conventional impact restraints is that the space between the shear plates should remain free of obstructions that could inhibit the movement of the hook and leg extension.
The present invention is intended to resolve these and other problems.